Touch-sensitive and hover-sensitive screens typically report the presence of an object using an (x,y) co-ordinate for a touch-sensitive screen and an (x,y,z) co-ordinate for a hover-sensitive screen. Some touch-sensitive screens may also report an inferred angle of incidence between an object and a screen. This angle of incidence may be used to estimate direction information associated with the object. For example, a conventional model may describe a finger touching a screen using five parameters (e.g., x, y, w, θp, θy) as illustrated in FIG. 21. While the x and y information may have been based on actual touch sensors, the w, θp, and θy information may have been inferred or estimated. However, these inference-based systems may have produced ambiguities in estimating positions based on contact location and shape, or based on a finger landing process, or based on Euler angles and geometry.
Touch-sensitive screens may then have taken actions based on the inferences concerning an intended touch point and the estimated position of a finger producing the intended touch point. For example, based on the inferences or estimations, text on a screen may have been wrapped around an area that may have been estimated to be occluded by the finger. Conventionally, attempts to detect finger angle may have required sensors located external to the screen. For example, a set of cameras that are positioned to image the area above the screen may have been employed to detect the angle of a finger. Or, conventional systems may have relied on detecting both a physical contact of a stylus as well as the proximity of other portions of a stylus. The use of external cameras or other external systems may have limited conventional systems to fixed table-top systems.